Stock-Based Compensation - RSA, RSU (Details) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2015 USD ($) $ / shares shares
Weighted Average Grant Date Fair Value
Expense recognition period	4 years
Restricted Stock Awards
Number of Shares
Number of Shares, Restricted Stock outstanding, Beginning Balance	83,028
Number of Shares, Vested	(28,943)
Number of Shares, Forfeited	(3,500)
Number of Shares, Restricted Stock outstanding, Ending Balance	50,585
Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Beginning Balance | $ / shares	$ 27.06
Weighted Average Grant Date Fair Value, Vested | $ / shares	26.56
Weighted Average Grant Date Fair Value, Forfeited | $ / shares	28.69
Weighted Average Grant Date Fair Value, Ending Balance | $ / shares	$ 27.24
Unrecognized compensation expense | $	$ 0.7
Weighted-average period for recognition of compensation cost	1 year 4 months 24 days
Restricted Stock Units
Number of Shares
Number of Shares, Restricted Stock outstanding, Beginning Balance	786,797
Number of Shares, Granted	558,678
Number of Shares, Vested	(419,895)
Number of Shares, Forfeited	(26,254)
Number of Shares, Restricted Stock outstanding, Ending Balance	899,326
Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Beginning Balance | $ / shares	$ 29.17
Weighted Average Grant Date Fair Value, Granted | $ / shares	38.40
Weighted Average Grant Date Fair Value, Vested | $ / shares	27.32
Weighted Average Grant Date Fair Value, Forfeited | $ / shares	35.18
Weighted Average Grant Date Fair Value, Ending Balance | $ / shares	$ 35.60
Unrecognized compensation expense | $	$ 14.0
Weighted-average period for recognition of compensation cost	2 years 2 months 12 days
Vesting Two Years From January 31 of Grant Year | Restricted Stock Units
Weighted Average Grant Date Fair Value
Stock incentive plan, vesting period	24 months
Vesting percentage	50.00%
Vesting Three Years From January 31 of Grant Year | Restricted Stock Units
Weighted Average Grant Date Fair Value
Stock incentive plan, vesting period	36 months
Vesting percentage	25.00%
Vesting Four Years From January 31 of Grant Year | Restricted Stock Units
Weighted Average Grant Date Fair Value
Stock incentive plan, vesting period	48 months
Vesting percentage	25.00%
Performance Restricted Stock Units [Member]
Number of Shares
Number of Shares, Granted	246,544
Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Granted | $ / shares	$ 38.45